Solved
STM32F4 doesn't capture correct number of pulses
Posted on April 25, 2017 at 19:09
Hello:
I'm using an STM32F4 to capture low frequency pulses below 50Hz. The source is sending exactly 20 pulses, with a DC of about 25%. The input pin to the STM32F4 confirms 20 pulses. However, the STM32F4 seems to capture only half of them -10. (i.e., I printf the T2_TIM2Freq value and see only 10 statements) If I set the source to burst 16 pulses, it captures (prints) 8. Here's the setup and the interrupt. Can someone see something that would cause this?
Thanks,
Gary
void TIM2configurationPA5(void)
{ NVIC_InitTypeDef NVIC_InitStructure; GPIO_InitTypeDef GPIO_InitStructure; TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; /* TIM2 Periph clock enable */ RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE); /* TIM2 channel 1 pin (PA.5) configuration */ GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; GPIO_InitStructure.GPIO_Speed = GPIO_High_Speed; GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; GPIO_Init(GPIOA, &GPIO_InitStructure); /* Connect TIM pins to AF2 */ GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_TIM2); TIM_TimeBaseStructInit(&TIM_TimeBaseStructure); TIM_TimeBaseStructure.TIM_Prescaler = 0; TIM_TimeBaseStructure.TIM_Period = (uint32_t)0xFFFFFFFF; TIM_TimeBaseStructure.TIM_ClockDivision = 0; TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Down; TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure); NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); TIM_ICInitStructure.TIM_Channel = TIM_Channel_1; TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising | TIM_ICPolarity_Falling; TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI; TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1; TIM_ICInitStructure.TIM_ICFilter = 0x0; TIM_ICInit(TIM2, &TIM_ICInitStructure); /* TIM enable counter */ TIM_Cmd(TIM2, ENABLE);/* Enable the CC2 Interrupt Request */
TIM_ITConfig(TIM2, TIM_IT_CC1, ENABLE); }void TIM2_IRQHandler(void)
{ if(TIM_GetITStatus(TIM2, TIM_IT_CC1) == SET) { /* Clear TIM2 Capture compare interrupt pending bit */ TIM_ClearITPendingBit(TIM2, TIM_IT_CC1); if(T2_captureNumber == 0) { T2_readValue1 = TIM_GetCapture1(TIM2); T2_captureNumber = 1; } else if(T2_captureNumber == 1) { T2_readValue2 = TIM_GetCapture1(TIM2); if (T2_readValue2 > T2_readValue1) { T2_uwCapture = (T2_readValue1 - T2_readValue2); } else if (T2_readValue2 < T2_readValue1) { T2_uwCapture = ((0xFFFFFFFF - T2_readValue2) + T2_readValue1); } else { T2_uwCapture = 0; }T2_TIM2Freq = (float32_t) (((SystemCoreClock / 2)/1.0) / (T2_uwCapture/1.0));
T2_captureNumber = 0; } }}